1. Field of the Invention
This invention relates to a cleaning device using fine frozen particles, which performs cleaning by spraying fine frozen particles, obtained by freezing water or the like, on an object to be cleaned.
2. Description of the Related Art
FIG. 2 is a side cross sectional view schematically showing the internal structure of a conventional cleaning device using fine frozen particles. The device shown includes an ice making section 10 equipped with a double-walled ice making container 1 composed of an inner and an outer ice making hopper 1a and 1b. The inner space of the inner ice making hopper 1a is refrigerated by a refrigerant 2 such as liquid nitrogen, and the space between the inner and outer ice making hoppers 1a and 1b is also filled with refrigerant 2, thus refrigerating the inner ice making hopper 1a from the outside as well. Liquid, such as extrapure water, is sprayed through a spray nozzle 3 into the inner ice making hopper 1a and is frozen so as to become fine frozen particles 4. A cleaning section 20 is equipped with a cleaning container 7, in which the fine frozen particles 4 produced in the ice making section 10 are sprayed on an object 6 to be cleaned by means of a spray gun 5.
The operation of this device will now be described. The inner space of the inner ice making hopper 1a is refrigerated by the refrigerant 2 filling the space between the outer and inner ice making hoppers 1a and 1b as well as by the refrigerant injected into the inner ice making hopper 1a. When, in this condition, liquid is sprayed by the spray nozzle 3, fine frozen particles 4 are produced. The thus produced fine frozen particles 4 are transferred to the spray gun 5, which is of the ejector type using a carrier 2a such as nitrogen or compressed dry air. By the jet stream force of the carrier gas 2a, the fine frozen particles 4 are sprayed on the object 6 to be cleaned, thereby cleaning the surface of the object 6. The fine frozen particles 4 sprayed from the spray gun 5, the carrier gas 2a, etc. are discharged out of the cleaning container 7 through an exhaust outlet 8. Accordingly, the fine particles 4 hit the surface of the object 6, causing any contaminants (not shown) thereon to be removed and discharged out of the container. The speed at which the fine frozen particles are sprayed by the spray gun 5 is adjusted by controlling the jet pressure of the carrier gas 2a. Further, the divergence of the spray steam of the fine frozen particles 4 from the spray gun 5 is determined by the configuration of the jet nozzle (not shown) of this spray gun 5.
Because of the above-described conventional cleaning devise using fine frozen particles employs an ejector-type spray gun, which utilizes a carrier-gas jet stream as the means of spraying the fine frozen particles on the object to be cleaned, it has been difficult to precisely control the speed, direction and divergence of the spray stream as well as the grain size of the fine frozen particles. Further, during the spraying, the jetting of the carrier gas causes the airflow inside the cleaning section to be disturbed, with the result that the contaminants removed from the object are blow around, thus allowing them to adhere to the object again.